Protein and nucleic acid delivery vehicles, components and mechanisms thereof

ABSTRACT

Complex viruses are assembled from simple protein subunits by sequential and irreversible assembly. During genome packaging in bacteriophages, a powerful molecular motor assembles at the special portal vertex of an empty prohead to initiate packaging. An aspect of the invention relates to the phage T4 packaging machine being highly promiscuous, translocating DNA into finished phage heads as well as into proheads. Single motors can force exogenous DNA into phage heads at the same rate as into proheads and phage heads undergo repeated initiations, packaging multiple DNA molecules into the same head. This shows that the phage DNA packaging machine has unusual conformational plasticity, powering DNA into an apparently passive capsid receptacle, including the highly stable virus shell, until it is full. These features allow for the design of a novel class of nanocapsid delivery vehicles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority to U.S. Provisional PatentApplication No. 61/322,334 entitled a “A Promiscuous DNA PackagingMachine from Bacteriophage T4” filed Apr. 9, 2010, the entire contentsand disclosure of which is incorporated herein by reference.

GOVERNMENT INTEREST STATEMENT

The United States Government has rights in this invention pursuant tofunding obtained from the National Institutes of Health (NIH) grantNIBIB 1R21 EB009869-01 and National Science Foundation grantMCB-0923873.

BACKGROUND

1. Field of the Invention

The present invention relates generally to protein and nucleic aciddelivery components, compositions, mechanisms and methods of deliverythereof.

2. Related Art

The packaging competency of a matured capsid shell has not beendiscovered. There is still much to be desired for improved vehicles ofgene therapy, especially for platforms that can deliver both nucleicacids and proteins. Outstanding issues relate to inefficiency of genepackaging, low amounts of genetic material being delivered, poortargeting and lack of tissue specificity. Other methods being employedfor delivery of nucleic acids and proteins have a number of limitations:for example, the injection of naked DNA has very low expression;electroporation has a high rate of cell death associated with it; manyviral vectors can only carry a small amount of nucleic acid fordelivery; and there may be dose-related toxicity associated withcationic liposomal delivery. There is a need for a platform to bedeveloped that addresses these issues.

SUMMARY

According one broad aspect, the present invention provides a methodcomprising the following steps: (a) attaching a packaging motor to acarrier and (b) transferring an exogenous material into an innercompartment of the carrier to thereby form a packaging machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary embodiments of theinvention, and, together with the general description given above andthe detailed description given below, serve to explain the features ofthe invention.

FIG. 1 is a schematic illustration showing DNA packaging by sequentialassembly and promiscuous assembly.

FIG. 2 is a photo showing the isolation of phage heads by differentialcentrifugation followed by CsCl gradient centrifugation.

FIG. 3 is a graph showing the peak associated with purification ofpartial heads by DEAE-Sepharose column chromatography.

FIG. 4 is an image of an SDS-PAGE gel showing separation of heads atdifferent stages.

FIG. 5 is an image of a western blot membrane probed with Gp17antibodies.

FIG. 6 is an image of a gel showing phage heads treated with DNAse Iand/or proteinase K and subjected to agarose gel electrophoresis andstained with cyber green.

FIG. 7 is an image of a gel showing the packaging of short DNA fragmentsinto phage heads under different conditions like with and without DNAand with and without Gp17.

FIG. 8 is an image of a gel showing the packaging of short DNA fragmentsinto phage heads under different conditions like with and without DNA,with and without Gp17 and with and without ATP.

FIG. 9 is an image showing the gradient following differentialcentrifugation of phage heads that were lysed in the presence of DNAase.

FIG. 10 is an image of an SDS-PAGE gel showing the concentration ofparticles used in the packaging reactions.

FIG. 11 is an image of a gel in which full head bands from the gradientwere treated with proteinase K and electrophoresed on a polyacrylamidegel.

FIG. 12 is an image of a gel in which partial head bands from thegradient were treated with proteinase K and electrophoresed on apolyacrylamide gel.

FIG. 13 is a schematic illustration showing the dual optical trap setupfor single molecule DNA packaging.

FIG. 14 is a graph showing the packaging of DNA by proheads.

FIG. 15 is a graph showing the packaging of DNA by partial heads.

FIG. 16 is a graph showing the packaging of DNA by full heads.

FIG. 17 is a graph showing the packaging of DNA by full heads.

FIG. 18 is a graph showing the packaging of DNA by full heads.

FIG. 19 is a schematic image showing the quantification of fluorescenceimages of immobilized T4 heads packaged with Cy3 DNA.

FIG. 20 is a schematic image showing the quantification of fluorescenceimages of immobilized T4 heads packaged with Cy5.

FIG. 21 is a histogram showing the number of heads packaged with Cy3 DNAin a single molecule fluorescence assay.

FIG. 22 is a histogram showing the number of heads packaged with Cy5 DNAin a single molecule fluorescence assay.

FIG. 23 shows representative images of partial heads, proheads, or fullheads packaged with Cy5 39-bp DNA.

FIG. 24 shows representative images of partial heads, proheads, or fullheads packaged with Cy3 83-bp DNA.

FIG. 25 is a normalized histogram showing single-head intensity forpartial heads and proheads.

FIG. 26 is a graph showing the typical photobleaching steps from asingle immobilized packaged head, packaged with multiple Cy5-labeled DNAfragments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Terminology

Where the meaning of terms departs from the commonly used meaning of theterm, applicant intends to utilize the terminology provided below,unless specifically indicated.

For purposes of the present invention, the term “bacteriophagecomponent” refers to bacteriophages and bacteriophage derivatives,including bacteriophages and bacteriophage derivatives having antigens,fusion proteins and other types of molecules attached thereto. Forexample, the term “T4 bacteriophage component” refers to T4bacteriophages and T4 bacteriophage derivatives.

For purposes of the present invention, the term “bacteriophagederivative” refers to any structure including at least part of theprotein coat of a bacteriophage. An example of a bacteriophagederivative is where foreign DNA is packaged into a customizedbacteriophage's genome is described, for example, in Jiang et al.,“Display of a PorA Peptide form Neisseria meningitidis on theBacteriophage T4 Capsid surface,” Infection and Immunity 65:4770-77(1997), Clark J R and March J B, “Bacteriophage-mediated nucleic acidimmunization,” FEMS Immunology and Medical Microbiology, 40, 21-26(2004) and March et al., “Genetic immunisation against hepatitis B usingwhole bacteriophage lambda particles,” Vaccine, 22, 1666-71 (2004), theentire contents and disclosures of which are incorporated herein byreference. Another example of a bacteriophage derivative is abacteriophage capsid. Another example of a bacteriophage derivative is abacteriophage tail. In one embodiment of the present invention, foreignDNA may be loaded into empty T4 capsids using the methods described inKondabagil et al., “The DNA translocating ATPase Of bacteriophage T4packaging motor,” J. Mol. Biol., 363: 786-99 (2006), the entire contentsand disclosures of which are incorporated herein by reference.

For purposes of the present invention, the term “bind,” the term“binding” and the term “bound” refers to any type of chemical orphysical binding, which includes but is not limited to covalent binding,hydrogen binding, electrostatic binding, biological tethers,transmembrane attachment, cell surface attachment and expression.

For purposes of the present invention, the term “biological sample” andthe term “biological specimen” refers to either a part or the whole of ahuman, animal, microbe or plant in vitro or in vivo. The term includesbut is not limited to material of human, animal, microbe or plant originsuch as human, animal, microbial or plant tissue sections, cell ortissue cultures, suspension of human, animal, microbial or plant cellsor isolated parts thereof, human or animal biopsies, blood samples,cell-containing fluids and secretion.

For purposes of the present invention, the term “capsid coat protein”refers to the proteins that come together in many copies to form acapsid shell of a virus. For example, the T4 bacteriophage capsid isconstituted by 930 copies of a single major capsid protein, gp23 (46kDa). The capsid also consists of 55 copies of another minor capsidprotein located at eleven of the 12 vertices (one pentamer at eachvertex) of the minor capsid protein gp24 (42 kDa). Structural studieshave established that two additional proteins, namely Hoc (Highlyantigenic outer capsid protein, 40 kDa) and Soc (Small outer capsidprotein, 9 kDa), are added onto the capsid after completion of capsidassembly Hoc is present up to 155 copies per capsid particle, whereasSoc is present up to 810 copies per capsid particle. These proteins maybe considered nonessential. Mutations in either of the genes, or in boththe genes, do not affect phage production, phage viability, phageinfectivity, or phage stability under normal experimental conditions.However, Hoc and Soc provide additional stability to the capsid underextreme environmental conditions. Capsid coat proteins of the T4bacteriophage and other phages are described, for example, in U.S.Patent Application. No. 2005/0226892 to Rao, entitled, “Methods andcompositions comprising bacteriophage nanoparticles,” published Oct. 13,2005, the entire contents and disclosure of which in incorporated hereinby reference.

For purposes of the present invention, the term “capsid” and the term“capsid shell” refers to the protein shell of a virus comprising severalstructural subunits of proteins. The capsid encloses the nucleic acidcore of the virus. The terms “prehead,” “prohead” or “procapsid,”“partial head” or “partially filled head,” “full head” and “phage head”in singular or plural form, refer to different stages of maturity of theviral capsid shell. “Prehead” refers to a capsid shell of precisedimensions or an isometric capsid that is initially assembled, oftenwith a single type of protein subunit polymerizing around a proteinscaffold. When the protein scaffolding is removed, creating an emptyspace inside the capsid shell, the structure is referred to as a proheador a procapsid. Partial head, full head and phage head all refer tocapsids that reach a stage of maturation that makes them larger, stablerparticles associated with DNA. The term “partial head” refers to amature capsid shell that either has only a portion of DNA packaged intoit or it may refer to a mature capsid shell that was once packed fullwith DNA and then the DNA releases from the shell to leave only a smallportion of DNA behind. The term “full head” refers to a mature capsidshell that is fully packed with DNA. Full heads can pack up to 105% ofthe bacteriophage genome. This is about 165-170 kb for T4bacteriophages. Similarly, capsids of other viruses can also be packagedto accommodate more than their genomic volume. The capsid may or may notbe enveloped. The maturation process of capsids in bacteriophages likeHK97 is described, for example, in Lata et al., “Maturation Dynamics ofa Viral Capsid: Visualization of Transitional Intermediate States,”Cell. 100(2), 253-263 (2000), as well as in Gertsman et al., “Anunexpected twist in viral capsid maturation,” Nature, 458, 646-50(2009), and in bacteriophages like T4 in Rao et al., “Structure andassembly of bacteriophage T4 head,” Virol. J. 7:356 (2010), byreference.

For purposes of the present invention, the term “carrier” refers to anysupport structure that brings about the transfer of a component ofgenetic material or a protein. Genetic material includes but is notlimited to DNA, RNA or fragments thereof and proteins or polypeptidescomprise amino acids and include but are not limited to antigens,antibodies, ligands, receptors or fragments thereof. Carriers includebut are not limited to vectors such as viruses (examples include but arenot limited to retroviruses, adenoviruses, adeno-associated viruses,pseudotyped viruses, replication competent viruses, herpes simplexvirus), virus capsids, liposomes or liposomal vesicles, lipoplexes,polyplexes, dendrimers, macrophages, artificial chromosomes,nanoparticles, polymers and also hybrid particles, examples of whichinclude virosomes. Carriers may have multiple surfaces and compartmentsfor attachment and storage of components. These include but are notlimited to outer surfaces and inner compartments.

For purposes of the present invention, the term “epitope” refers to thesmallest part of an antigen moiety recognizable by the combining site ofan immunoglobulin.

For purposes of the present invention, the term “exogenous material”refers to material that originates outside the organism of concern ormaterial that may be isolated from a organism, manipulated to any extentexternally and then reintroduced into its natural environment or theenvironment from which it was isolated. Exogenous material includes butis not limited to nucleic acids, proteins, polymeric compounds,particulate matter and artificially synthesized material. For example,“exogenous nucleic acid” refers to any nucleic acid, DNA or RNA orfragments thereof, either single or double stranded, that originatesoutside of the organism of concern or was isolated from the organism,modified and reintroduced into the organism. Exogenous DNA present in ahost cell may be derived from a source organism, cloned into a vectorand then introduced into a host cell.

For purposes of the present invention, the term “immune response” refersto a specific response of the immune system of an animal to antigen orimmunogen. Immune response may include the production of antibodies andcellular immunity.

For purposes of the present invention, the term “immunity” refers to astate of resistance of a subject animal including a human to aninfecting organism or substance. It will be understood that an infectingorganism or substance is defined broadly and includes parasites, toxicsubstances, cancer cells and other cells as well as bacteria andviruses. A “Therapeutically Effective Immunization Course” (see belowfor definition) will produce the immune response.

For purposes of the present invention, the term “immunizationconditions” refers to factors that affect an immune response includingthe amount and kind of immunogen or adjuvant delivered to a subjectanimal including a human, method of delivery, number of inoculations,interval of inoculations, the type of subject animal and its condition.“Vaccine” refers to pharmaceutical formulations able to induce immunity.

For purposes of the present invention, the term “immunization dose”refers to the amount of antigen or immunogen needed to precipitate animmune response. This amount will vary with the presence andeffectiveness of various adjuvants. This amount will vary with theanimal and the antigen, immunogen and/or adjuvant but will generally bebetween about 0.1 μg/ml or less and about 100 μg per inoculation. Theimmunization dose is easily determined by methods well known to thoseskilled in the art, such as by conducting statistically valid hostanimal immunization and challenge studies as described: for example,Manual of Clinical Immunology, H. R. Rose and H. Friedman, AmericanSociety for Microbiology, Washington, D.C. (1980), tithe entire contentsand disclosures of which are incorporated herein by reference. In someinstances, several immunization doses including booster doses mayadministered to provide immunity, and, For purposes of the presentinvention such a course of treatment is collectively referred to as“Therapeutically Effective Immunization Course”.

For purposes of the present invention, the term “immunogen” and the term“immunogenic” refers to a substance or material (including antigens)that is able to induce an immune response alone or in conjunction withan adjuvant. Both natural and synthetic substances may be immunogens. Animmunogen is generally a protein, peptide, polysaccharide,nucleoprotein, lipoprotein, synthetic polypeptide, or hapten linked to aprotein, peptide, polysaccharide, nucleoprotein, lipoprotein orsynthetic polypeptide or other bacterial, viral or protozoal fractions.It will be understood that “immunogen” or a composition that is“immunogenic” includes substances (e.g., small peptides) that do notgenerate an immune response (or generate only a therapeuticallyineffective immune response) unless associated with an adjuvant. Forpurposes of the present invention, such immunogens are referred to as“adjuvant-obligatory” immunogens.

For purposes of the present invention, the term “immunogenic amount” isan amount of an antigen preparation of interest or amount of abiological toxin that elicits a clinically detectable protectiveresponse in an animal.

For purposes of the present invention, the term “liposome” and the term“liposomal vesicle” refers to a vesicle composed of a bilayer membrane,such as a bilayer membrane composed of a phospholipid and a cholesterolbilayer. Liposomes may also contain other steroid components such aspolyethylene glycol derivatives of cholesterol (PEG-cholesterols),coprostanol, cholestanol, or cholestane, and combinations of PC andcholesterol. Liposomes may also contain glycolipids. Aspects ofliposomes are further described in U.S. Patent Application No.2008/0274533 to Alving et al, entitled “T4 Bacteriophage Bound to aSubstrate,” published Nov. 6, 2008, the entire contents and disclosuresof which are incorporated herein by reference.

For purposes of the present invention, the term “neck protein” and theterm “tail protein” refers to proteins that are involved in the assemblyof any part of the necks or tails of a virus particle, in particularbacteriophages. Tailed bacteriophages belong to the order Caudoviralesand include three families: The Siphoviridae have long flexible tailsand constitute the majority of the tailed viruses. Myoviridae have longrigid tails and are fully characterized by the tail sheath thatcontracts upon phage attachment to bacterial host. The smallest familyof tailed viruses are podoviruses (phage with short, leg-like tails).For example, in T4 bacteriophage gp10 associates with gp11 to forms thetail pins of the baseplate. Tail pin assembly is the first step of tailassembly. The tail of bacteriophage T4 consists of a contractile sheathsurrounding a rigid tube and terminating in a multiprotein baseplate, towhich the long and short tail fibers of the phage are attached. Once theheads are packaged with DNA, the proteins gp13, gp14 and gp15 assembleinto a neck that seals of the packaged heads, with gp13 protein directlyinteracting with the portal protein gp20 following DNA packaging andgp14 and gp15 then assembling on the gp13 platform. Neck and tailproteins in T4 bacteriophage may include but are not limited to proteinsgp6, gp25, gp53, gp8, gp10, gp11, gp7, gp29, gp27, gp5, gp28, gp12, gp9,gp48, gp54, gp3, gp18, gp19, gp13, gp14, gp15 and gp63. Aspects of theneck and tail assembly proteins in T4 bacteriophage and other virusesare described further, for example, in Rossmann et al., “Thebacteriophage T4 DNA injection machine,” Curr. Opin. Struct. Biol.14(2):171-80 (2004), Kostyuchenko et al., “Three-dimensional structureof bacteriophage T4 baseplate,” Nat. Struct. Biol. 10(9):688-93 (2003),Tao et al., “Assembly of a tailed bacterial virus and its genome releasestudied in three dimensions,” Cell 95(3): 431-37 (1998), the entirecontents and disclosures of which are incorporated herein by reference.

For purposes of the present invention, the term “non-naturallyoccurring” or “isolated” refers to the component of interest being atleast substantially free from at least one other component with which itis naturally associated in nature and as found in nature.

For purposes of the present invention, the term “packaging machine”refers to the complete packaging unit including the compartment, themotor and the component or any other attachment mechanism that connectsthe motor to the compartment. For example, the T4 packaging machinecomprises the shell (the procapsid made primarily of gp23), the vertexportal protein (dodecameric gp20) and the gp17 packaging motor. The T4DNA packaging machine is further described, for example, in Zhang etal., “A promiscuous DNA packaging machine from bacteriophage t4,” PLoSBiol. 9(2):310000592 (2011), and in Rao et al., “DNA Packaging inBacteriophage T4,” Madame Curie Bioscience Database, Landes Bioscience,(2000), the entire contents and disclosures of which are incorporatedherein by reference.

For purposes of the present invention, the term “packaging motor” refersto a molecular motor or a molecular machine that is capable of usingchemical energy to drive the mechanical translocation of a nucleic acidand package the nucleic acid into a compartment. For example, thepackaging motor in T4 bacteriophage uses the energy of ATP hydrolysis totranslocate and package DNA into the capsid shell. The packaging motormay be a protein complex comprising one or more protein subunits andhave enzymatic activities that help package nucleic acids, whichinclude, but are not limited to ATPase, nuclease and translocase. Forexample, T4 bacteriophage packaging motor refers to a large terminaseprotein, the pentameric gene product (gp)17. The term “packaging motor”may also be considered to encompass additional proteins that regulate orenhance the activity of the actual motor. For example, the T4 packagingmotor may also include a small terminase protein gp16. The T4 DNApackaging motor is further described in, for example, Sun et al., “Thestructure of the phage T4 DNA packaging motor suggests a mechanismdependent on electrostatic forces,” Cell 135(7):1251-62 (2008), byreference.

For purposes of the present invention, the term “peptide-like” refers toshort chain peptides as well as proteins, lipoproteins andglycoproteins, but will also, for convenience, include non-proteinaceousmolecules, for example, amino acid-containing molecules. In certainembodiments, the peptide-like therapeutic agent may additionallycomprise vitamins, steroids, azidothymidine, and free primaquine inaddition to other agents. One useful class of peptides isimmunomodulators such as interleukins, colony stimulating factors andinterferons. Another useful class of proteins is antigens and immunogenssuch as are used in vaccines.

For purposes of the present invention, the term “purified” refers to thecomponent in a relatively pure state—e.g. at least about 90% pure, or atleast about 95% pure or at least about 98% pure.

For purposes of the present invention, the term “virus particle” refersto viruses and virus-like organisms.

DESCRIPTION

The present invention may be understood more readily by reference to thefollowing detailed description of specific embodiments included herein.Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details should be regarded as limitations upon the scope of theinvention. The entire text of the references mentioned herein andreferences cited within them are incorporated herein by reference intheir entireties including U.S. Provisional Patent Application No.61/322,334 entitled a “A Promiscuous DNA Packaging Machine fromBacteriophage T4” filed Apr. 9, 2010.

Phage T4 is a prototype for tailed bacteriophages, the most abundantorganisms on the planet, as well as for large eukaryotic viruses such asherpes viruses. These viruses encode powerful machines to package theirgenomes tightly inside an icosahedral-shaped capsid “head”. Packaginginto the capsid occurs via a dodecameric portal, localized in one of thevertexes of the capsid. Packaging requires precise orchestration of aseries of steps: assembly of an empty prohead, concatemer cutting andattachment of the motor-DNA complex to the portal vertex, ATP-fueled DNAtranslocation until the head is full, DNA cutting to terminatepackaging, detachment of the motor, and sealing of the packaged head by“neck” assembly. Sequential conformational changes, particularly in theportal, are thought to drive these transitions such that assemblyproceeds directionally and irreversibly.

In one embodiment, the present invention takes advantage of the newdiscovered fact that the phage T4 packaging machine on various capsidsis highly promiscuous, translocating DNA into proheads but also,unexpectedly, into previously filled virus heads. Other studies haveshown that in filled viral capsids the structure of the portal isfundamentally altered, and it was thought that the packaging mechanismon full heads would be irreversible. An aspect of the invention relatesto the showing that full heads, or heads that are emptied of most oftheir packaged DNA, can reassemble the packaging machine and use it tore-fill the capsid with any DNA molecules.

These results challenge the classic sequential virus assembly models,suggest an explanation for the evolution of viral genomes that fitcapsid volume, and point the way to a novel nanocapsid delivery systemin which the viral packaging machine (portal and motor) could be used totranslocate DNA and other therapeutic molecules into synthetic capsids.

In one embodiment, the present invention provides a T4 bacteriophagecomponent being used as a carrier to deliver nucleic acids and/orproteins of interest.

In one embodiment, the present invention provides a packaging motor thatis a T4 bacteriophage packaging motor.

In one embodiment, the present invention provides a T4 packaging motorthat can associate with a liposomal vesicle to package nucleic acidsinto the liposomal vesicle.

In one embodiment, the present invention provides a packaging motor thatcan associate with any compartment to which it is capable of attachingand package nucleic acids to the full volume capacity of thecompartment.

In one embodiment, the present invention provides a multiuse type ofdelivery vehicle that can be packaged with nucleic acids and attached toproteins of interest.

Tailed bacteriophages are ubiquitously distributed in nature and are themost abundant organisms on the planet as referred to in Hendrix,“Evolution: the long evolutionary reach of viruses,” Curr. Biol. 9:R914-R917 (1999). These, in particular, bacteriophage T4, are excellentmodels to elucidate the mechanisms of DNA condensation anddecondensation in living organisms. The virion consists of a head intowhich the genome is packaged, and a tail that delivers the genome intothe bacterial cell. The head is pressurized to ˜6 MPa—equivalent to morethan ten times the pressure inside a bottle of champagne—because of thepacking of highly negatively charged, relatively rigid double-strandedDNA (dsDNA) to near crystalline density (˜500 μg/ml) further describedin Smith et al., “The bacteriophage straight phi29 portal motor canpackage DNA against a large internal force,” Nature 413: 748-52 (2001);and Lander et al., “The structure of an infectious P22 virion shows thesignal for headful DNA packaging,” Science 312: 1791-95 (2006).

Common pathways and mechanisms are involved in building dsDNA viruses asdescribed in Casjens, “Control mechanisms in dsDNA bacteriophageassembly,” The Bacteriophages, Volume 1, Calendar R, editor, New York:Plenum Press, 15-91 (1988), Black et al., “Morphogenesis of the T4head,” Molecular biology of bacteriophage T4, Karam, editor, Washington,D.C.: American Society for Microbiology, 218-58 (1994), and Mettenleiteret al., “Herpesvirus assembly: an update,” Virus Res. 143: 222-234(2009). A capsid of precise dimensions is first assembled, often with asingle type of protein subunit polymerizing around a protein scaffold(FIG. 1). A cone-shaped dodecameric portal initiates assembly andremains at the special five-fold vertex of the isometric capsid(prehead), facilitating all subsequent transactions: DNA entry, tailattachment, and DNA ejection as referred to in Simpson et al.,“Structure of the bacteriophage phi29 DNA packaging motor,” Nature 408:745-50 (2000); and Lebedev et al. “Structural framework for DNAtranslocation via the viral portal protein,” EMBO J. 26: 1984-94 (2007).The scaffold is removed, creating an empty space inside the capsid(prohead or procapsid) for encapsidating the viral genome (step A ofFIG. 1). A packaging ATPase motor, also known as the “terminase,”recognizes and cuts the concatemeric viral DNA and docks at the narrowprotruding end of the prohead portal, inserting the DNA end into the˜3.5-nm portal channel as described in Rao et al., “The bacteriophageDNA packaging motor,” Annu. Rev. Genet. 42: 647-81 (2008).

The packaging machine thus assembled drives DNA translocation utilizingthe free energy of ATP hydrolysis (step B of FIG. 1). After filling thehead (“headful” packaging), the motor cuts the DNA and dissociates fromthe DNA-full head (step C of FIG. 1) as referred to in Alam et al., “Theheadful packaging nuclease of bacteriophage T4,” Mol. Microbiol. 69:1180-90 (2008). The neck and tail proteins assemble on the portal,completing the infectious virus assembly (step D of FIG. 1) as describedin Rao, “A virus DNA gate: zipping and unzipping the packed viralgenome,” Proc. Natl. Acad. Sci., 106: 8403-04 (2009); Zheng et al., “Aconformational switch in bacteriophage p22 portal protein primes genomeinjection,” Mol. Cell. 29: 376-83 (2008); Bode et al., “The arrangementof DNA in lambda phage heads. I. Biological consequences of micrococcalnuclease attack on a portion of the chromosome exposed in taillessheads,” J. Mol. Biol. 62: 493-502 (1971); Lhuillier et al., “Structureof bacteriophage SPP1 head-to-tail connection reveals mechanism forviral DNA gating,” Proc. Natl. Acad. Sci. 106: 8507-12 (2009); and Edgaret al., “Morphogenesis of bacteriophage T4 in extracts ofmutant-infected cells,” Proc. Natl. Acad. Sci. 55: 498-505 (1966).

The phage T4 packaging motor is the fastest and most powerful reportedto date. It generates ˜60 pN of force and packages at a rate of up to2,000 bp/s. The motor is composed of a large terminase protein, gp17 (70kDa), and a small terminase protein, gp16 (18 kDa) as described in Raoet al., “Cloning, overexpression and purification of the terminaseproteins gp16 and gp17 of bacteriophage T4. Construction of a definedin-vitro DNA packaging system using purified terminase proteins,” J.Mol. Biol. 200: 475-88 (1988). gp17 contains all the enzymaticactivities necessary for DNA packaging: ATPase, nuclease, andtranslocase as described in Leffers et al., “Biochemicalcharacterization of an ATPase activity associated with the largepackaging subunit gp17 from bacteriophage T4,” J. Biol. Chem. 275:37127-136 (2000); Rentas et al., “Defining the bacteriophage T4 DNApackaging machine: evidence for a C-terminal DNA cleavage domain in thelarge terminase/packaging protein gp17,” J. Mol. Biol. 334: 37-52(2003); and Baumann et al., “Isolation and characterization of T4bacteriophage gp17 terminase, a large subunit multimer with enhancedATPase activity,” J. Biol. Chem. 278: 4618-27 (2003). Five molecules ofgp17 assemble on the portal, forming a pentameric motor with a centraltranslocation channel that is continuous with the portal channel asdescribed in Sun et al., “The structure of the phage T4 DNA packagingmotor suggests a mechanism dependent on electrostatic forces,” Cell 135:1251-1262 (2008). Gp16, a putative 1′-mer, regulates gp17's activities,but its location on the packaging machine is unknown as described in vanDuijn, “Current limitations in native mass spectrometry based structuralbiology,” J. Am. Soc. Mass. Spectrom. 21: 971-78 (2010); and Al-Zahraniet al., “The small terminase, gp16, of bacteriophage T4 is a regulatorof the DNA packaging motor,” J. Biol Chem 284: 24490-500 (2009).Structural and biochemical studies suggest that packaging is driven bythe electrostatic force generated by the motor alternating betweenrelaxed and tensed conformational states.

A fundamental feature of virus assembly is “sequential assembly” inwhich “simple” components assemble in a strict sequence to generate acomplex nanomachine with unique biological properties. Each assemblystep generates a new site or conformational state to which the nextcomponent binds with exquisite specificity, essentially irreversibly asdescribed in Wood, “Bacteriophage T4 morphogenesis as a model forassembly of subcellular structure,” Q. Rev Biol. 55: 353-67 (1980). Aseries of such steps, as documented by studies in phage T4, referred toin King, “Assembly of the tail of bacteriophage T4,” J. Mol. Biol. 32:231-62 (1968), and numerous other viruses leads to rapid andhigh-fidelity assembly of a complex infectious virion as described inCasjens et al., “Control mechanisms in dsDNA bacteriophage assembly,”The bacteriophages, Volume 1, Calendar, editor, New York: Plenum Press,15-91 (1988). In phage T4, this process assembles virions approaching atheoretical infection efficiency of 1.

The sequence of steps in the head morphogenesis of phage T4 (in vivo),as well as in other phages and dsDNA viruses (e.g., herpes viruses), isas follows: (i) assembly of the packaging motor on a nascent(unexpanded) empty prohead (step A of FIG. 1), (ii) expansion of thecapsid after about 10%-25% of the genome is packaged (step B of FIG. 1),(iii) packaging until the head is full, (iv) cutting of DNA anddissociation of the motor (step C of FIG. 1), and (v) assembly of neckproteins to seal the packaged heads (step D of FIG. 1). Conformationalchanges in the portal are reported to drive these sequentialirreversible transitions (FIG. 1; the portal goes through differentconformational states in each stage)

An advantageous aspect of the invention relates to the assembly of thephage T4 genome packaging machine not strictly adhering to the paradigmof sequential and irreversible steps (“motor” refers to pentameric gp17;whereas “machine” refers to the complete packaging unit including shell[gp23], portal, and motor). Results show that the assembly of the phageT4 packaging machine is highly promiscuous and does not discriminate asto the type of head it assembles on. In one embodiment of the invention,the motor can translocate into the phage head, either the DNA-full head(step G of FIG. 1) or the once full but DNA-ejected head (step F of FIG.1). In fact, the latter shows 5- to 10-fold greater packaging efficiencythan the prohead. This is the first report demonstrating that a finishedvirus shell can reassemble the packaging machine and repackage any DNA.Single molecule optical tweezers experiments are used to show anotherembodiment of the invention, that the packaging rate ofphage-head-assembled packaging machines is similar to that of machinesassembled on packaging-naïve proheads. Single molecule fluorescencemeasurements show a further embodiment of the invention that the maturephage heads catalyze repeated packaging initiations, encapsidatingmultiple DNA molecules within the same head. An advantageous embodimentof the invention is that the phage T4 DNA packaging machine has unusualconformational plasticity, powering genome translocation into a passivecapsid receptacle regardless of its maturation stage. These features mayhave driven the evolution of headful measured genomes in dsDNA viruses,and may offer avenues to further embodiments of the invention like thedesign novel nanodevices that can transport DNA therapeutics andvaccines into cells.

One of the central themes in virus assembly is sequential andirreversible assembly. Assembly of one component generates a new site orconformational state that is specific for the assembly of the nextcomponent and so on as further described in Casjens et al., “Controlmechanisms in dsDNA bacteriophage assembly, The bacteriophages, Volume1, Calendar, editor, New York: Plenum Press, 15-91 (1988); and King,“Assembly of the tail of bacteriophage T4,” J. Mol. Biol. 32: 231-62(1968). If a component is missing, assembly proceeds up to that pointand stalls, accumulating a partially assembled structure and unassembleddownstream components as further described in Edgar et al.,“Morphogenesis of bacteriophage T4 in extracts of mutant-infectedcells,” Proc. Natl. Acad. Sci. 55: 498-505 (1966) and Kikuchi et al.,“Genetic control of bacteriophage T4 baseplate morphogenesis. I.Sequential assembly of the major precursor, in vivo and in vitro,” J.Mol. Biol. 99: 645-72 (1975). Although the precise mechanisms are stillpoorly understood, the assembled structure does not spontaneouslydisassemble, nor is it in equilibrium with the unassembled subunits,presumably because it is locked in a different, energetically stable,conformational state. This process not only ensures directional assemblyin a predetermined order but also leads to rapid and high-fidelityconstruction of a complex infectious virion from the seemingly chaoticdistribution of subunits in the infected cell.

Sequential conformational changes in the portal and the major capsidprotein may drive maturation transitions from the nascent prohead to theDNA-full head as suggested in Casjens et al., “Control mechanisms indsDNA bacteriophage assembly,” The bacteriophages, Volume 1, Calendar,editor. New York: Plenum Press. 15-91 (1988); Black et al.,“Morphogenesis of the T4 head,” Molecular biology of bacteriophage T4,In: Karam, editor, Washington, D.C.: American Society for Microbiology,218-58 (1994); and Rao, “A virus DNA gate: zipping and unzipping thepacked viral genome,” Proc. Natl. Acad. Sci. 106: 8403-404 (2009). Theseinclude assembly of the packaging motor, packaging initiation, proheadexpansion, headful packaging, packaging termination, and assembly ofneck proteins (FIG. 1, steps A to D).

The major capsid protein gp23 undergoes a major conformational changeduring prohead expansion, leading to a ˜15% increase in outer dimensionsand a ˜50% increase in inner volume (gp23 is the cleaved form of themajor capsid protein gp23; cleavage occurs during maturation of preheadto prohead; as indicated in FIG. 1, step A). A conformational change inthe T4 portal gp20 was reported to trigger this expansion followingassembly of packaging motor on the unexpanded prohead as referred to inRay et al., “Portal control of viral prohead expansion and DNApackaging,” Virology 391: 44-50 (1999). About 870 binding sites for Soc(small outer capsid protein) and 155 binding sites for Hoc (highlyantigenic outer capsid protein) are exposed following the expansiontransition as described in Carrascosa, “Head maturation pathway ofbacteriophages T4 and T2. IV. In vitro transformation of T4 head-relatedparticles produced by mutants in gene 17 to capsid-like structures,” J.Virol. 26: 420-28 (1978).

In phages SPP1 and P22, portal conformational variants were shown toeither underpackage (˜95% of genome per head), or overpackage (˜105% ofgenome per head) the head as referred to in Orlova et al., “Structure ofthe 13-fold symmetric portal protein of bacteriophage SPP1,” Nat.Struct. Biol. 6: 842-846 (1999); and Casjens et al., “Bacteriophage P22portal protein is part of the gauge that regulates packing density ofintravirion DNA,” J. Mol. Biol. 224: 1055-74 (1992). In phage P22, apiece of packaged DNA spools around the portal, forcing a conformationalchange that apparently signals the motor to make the headful terminationcut and disengage from the DNA-full head. Another portal conformationalchange primes DNA delivery following the binding of neck proteins. Thus,as was appreciate in the art at the time of the invention, the DNA-fullheads, having just ejected the packaging motor following head filling,would not be competent to reinitiate packaging; instead, these would beprimed to bind the neck proteins. Applicants show that, for the firsttime, the packaging machine assembly is neither sequential norirreversible. It can occur on the finished head as efficiently as on thepackaging-naïve empty (unexpanded or expanded) prohead, as wasdemonstrated by bulk as well as single molecule experiments. Suchpromiscuous assembly appears to be a special property of the packagingmachine because all other head assembly transitions (for example, headexpansion) are irreversible and follow the classic sequential assemblyparadigm. The fact that the motor can translocate DNA into the capsidregardless of its maturation state—unexpanded, expanded, DNA-full, orDNA-ejected—suggests that the shell as such is a passive receptacle. Themain goal of the packaging process appears to be to power genome into acapsid receptacle until it is full.

What is the structural basis for the conformational plasticity of thepackaging machine? X-ray and cryo-electron microscopy structures showthat despite lacking sequence similarity, the three-dimensionalstructure of the portals is strictly conserved as described inMettenleiter et al., “Herpesvirus assembly: an update,” irus. Res. 143:222-34 (2009) and Simpson et al., “Structure of the bacteriophage phi29DNA packaging motor,” Nature 408: 745-750 (2000). The cone-shaped portalconsists of three parts: a wide domain that is inside the icosahedralvertex, a long central stem that forms the channel, and a stalk thatprotrudes out of the capsid. The channel is lined by α-helices radiatingfrom the center at a ˜45° angle, whereas the protruding end has an α/βdomain connected by loops. In one model, the portal may oscillatebetween different energetically equivalent conformational states butgets “frozen” in one state upon binding to a partner molecule, gp17,gp13, etc. In another model, different binding sites may be accessibleat different stages of the maturation pathway. In the nascent procapsid,only the protruding stalk would be accessed, allowing the assembly ofgp17, but after head filling, the internal pressure of packaged DNAmight push the portal down, exposing part of the stem that containsbinding sites for neck proteins. Neck protein assembly displaces thepackaging motor, but in the absence of neck proteins the packaging motorcan reassemble to the portal.

A promiscuous packaging machine may have led to the evolution of headfulgenomes, a fundamentally common feature among dsDNA phages and viruses,including the herpes viruses as referred to in Rao et al., “Thebacteriophage DNA packaging motor,” Annu. Rev. Genet. 42: 647-81 (2008).Closed shells assembled from an ancient capsid protein probably predatesgenome evolution. A flexible packaging machine that can indiscriminatelytranslocate DNA molecules into a capsid receptacle would continuepackaging until the capsid is full. The filled shells, by virtue of theenergy (internal pressure) present in the tightly packed DNA, can moreefficiently deliver the “genome” into a host cell. Eventually, thisselective advantage leads to the evolution of infectious capsids(virions) whose interior is tightly packed with DNA, their lengthdictated by the internal volume of the closed shell. An advantageousembodiment of the invention is to tightly package DNA to efficientlydeliver exogenous material into a host cell, under either in vitro or invivo conditions.

The conformational flexibility of the packaging machine may also lead tomore efficient production of infectious virions in a normal infection.The low-abundant packaging/terminase proteins must compete for the DNAsubstrate with a variety of other DNA metabolizing enzymes involved intranscription, replication, recombination, and repair. Should thepackaging motor prematurely fall off, or be displaced from the head, itcould reassemble and resume packaging.

In another embodiment of the invention, highly stable virus shells areused as packaging containers. This is a significant breakthrough from atechnical standpoint and has broad implications. First, the proheadscurrently used in all the in vitro DNA packaging systems are veryfragile, and in T4 the prohead is a heterogeneous mixture of unexpanded,expanded, damaged, and partially Soc/Hoc-bound particles. In anembodiment of the invention, the heads that have undergone all thematuration transitions are homogenous and structurally very stable andreinforced with 870 copies of Soc, offering a very efficient system topackage DNA as well as generate high-resolution reconstructions ofpackaging intermediates. Another embodiment of the invention is thatpartial heads have 5- to 10-fold greater packaging efficiency than theproheads. In an advantageous embodiment of the invention, it is possibleto overcome some of the technical barriers to developing in vitro DNApackaging systems for eukaryotic viruses such as herpes viruses andadenoviruses by ejecting the packaged DNA from the virions as describedin Newcomb et al., “Polarized DNA ejection from the herpesvirus capsid,”J. Mol. Biol. 392: 885-94 (2009), and repackaging different DNA into theemptied heads. In another embodiment of the invention, the powerfulpackaging motor can be used to encapsidate large chunks of foreign DNAand target these particles to specific cells or tissues by displayingspecific ligands on the capsid surface as referred to in Li et al.,“Bacteriophage T4 capsid: a unique platform for efficient surfaceassembly of macromolecular complexes,” J. Mol. Biol. 363: 577-88 (2006).Such particles can deliver multiple genes for gene therapy as well asmultivalent DNA vaccines against pathogenic agents. In a furtherembodiment of the invention the phage T4 head, which has very highcapacity (˜170 kb) and demonstrates ability to package multiple DNAmolecules in the same head, would be a particularly attractivenanoparticle. In another embodiment of the invention, nanomotors aredesigned for various biomedical applications. Since the shell appears tobe a passive receptacle, the packaging machine (portal and motor) couldbe stripped off of the capsid and inserted into an artificial and muchlarger shell, such as a liposome or mammalian cell, and the machinecould be made to translocate DNA and other therapeutic molecules intothese compartments.

The surface of bacteriophage T4 nanoparticles can be modified, eitherthrough genetic engineering or direct chemical conjugation to displayfunctional moieties such as antibodies or other proteins to recognize aspecific target and can be used as sensors as further described inArcher et al., Sensors, 9, 6298-311 (2009). Among the broad range ofplant and bacterial viruses that have been investigated, the interest inthe use phages and particularly bacteriophage T4 as a nano-material, hasrecently increased, due to its flexible, unrestricted display systemRao, V. B. Methods and compositions comprising bacteriophagenanoparticles as has been described in U.S. Patent Application. No.2005/0226892 to Rao, entitled, “Methods and compositions comprisingbacteriophage nanoparticles,” published Oct. 13, 2005; Li et al.,“Assembly of the small outer capsid protein, Soc, on Bacteriophage T4: Anovel system for high density display of multiple large anthrax toxinsand foreign proteins on phage capsid,” J. Mol. Biol. 370, 1006-10192007; Wu et al., “Bacteriophage T4 nanoparticle capsid surface SOC andHOC bipartite display with enhanced classical swine fever virusimmunogenicity: A powerful immunological approach,” J. Virol. Meth. 139,50-60 (2007).

Liposomes can be prepared in many different sizes, ranging from smallunilamellar vesicles (SW's), whose smallest dia. are about 20 nm, togiant unilamellar vesicles (GUV's) up to tens of pm in dia. In betweenare the multilamellar vesicles (MLV's); i.e. the first generation ofliposomes (l), of several hundreds of nm in dia., and the more recentlarge unilamellar vesicles (LUV's), characterized by high capturevolumes, whose dia. can be adjusted (e.g. 100 or 200 nm) and sizedistribution narrowed-down by extrusion through specific membranes (2).In essence, liposomes are highly versatile structures whose propertiescan be modulated by changing number of parameters such as size,lamellarity, composition of the bilayers, surface charges and surfaceproperties; for the chemist the (phospho)lipids which are theconstituents of liposomes are also challenging molecules for designinganalogs endowed with new properties and derivatives that are useful:e.g., for coupling ligands to the surface of the vesicles. Because ofthe polyanionic nature of DNA, cationic (and neutral) lipids aretypically used for gene delivery, while the use of anionic liposomes hasbeen fairly restricted to the delivery of other therapeuticmacromolecules as referred to in Mayhew et al., “Therapeuticapplications of liposomes,” Liposomes, Ostro, editor, Marcel Dekker: NewYork, 289-341 (1983).

In another embodiment of the invention, a carrier that encompassesbacteriophage T4 viruses or the T4 virus capsid can have mutations inany of the constituent protein subunits that may result in advantageousproperties in methods of gene therapy. The mutations may be introducedinto the nucleic acid sequences of the constituent carrier proteins. Thecarrier may also be used to deliver target genes or proteins that havealso be modified. For example, modifications can address issues like theshort-lived nature of gene therapy by generating nucleic acids that arelong lived and stable. Another modification can result in no or reducedimmune responses from the organism when exogenous material is introducedinto it. In addition, modifications can be made to address toxicity,immune and inflammatory responses and potential disease causing abilityof the carrier itself. Modification can also be made to addressmultigene disorders and to reduce the chance of tumor formation withinsertional mutagenesis. The terms “protein,” “peptide,” “polypeptide,”and “amino acid sequence” are used interchangeably herein to refer topolymers of amino acid residues of any length. The polymer may be linearor branched, it may comprise modified amino acids or amino acid analogs,and it may be interrupted by chemical moieties other than amino acids.The terms also encompass an amino acid polymer that has been modifiednaturally or by intervention; for example disulfide bond formation,glycosylation, lipidation, acetylation, phosphorylation, or any othermanipulation or modification, such as conjugation with a labeling orbioactive component.

The present invention also encompasses carriers into which polypeptideswith novel functions are introduced. For example, the novel function mayproceed via directed or random mutagenesis coupled with a functionalselection or screen. Methods of mutagenesis are well known to one ofskill in the art. As used herein the terms “nucleotide sequences” and“nucleic acid sequences” refer to deoxyribonucleic acid (DNA) orribonucleic acid (RNA) sequences, including, without limitation,messenger RNA (mRNA), DNA/RNA hybrids, or synthetic nucleic acids. Thenucleic acid can be single-stranded, or partially or completelydouble-stranded (duplex). Duplex nucleic acids can be homoduplex orheteroduplex.

As used herein the term “transgene” may be used to refer to“recombinant” nucleotide sequences that may be associated with thepresent invention. The term “recombinant” means a nucleotide sequencethat has been manipulated “by man” and that does not occur in nature, oris linked to another nucleotide sequence or found in a differentarrangement in nature. It is understood that manipulated “by man” meansmanipulated by some artificial means, including by use of machines,codon optimization, restriction enzymes, etc.

For example, in one embodiment the nucleotide sequences may be mutatedsuch that the activity of the encoded proteins in vivo is abrogated. Inanother embodiment the nucleotide sequences may be codon optimized: forexample, the codons may be optimized for human use. In preferredembodiments the nucleotide sequences of the invention are both mutatedto abrogate the normal in vivo function of the encoded proteins, andcodon optimized for human use.

As regards codon optimization, the nucleic acid molecules associatedwith the invention have a nucleotide sequence that encodes the antigensof the invention and can be designed to employ codons that are used inthe genes of the subject in which the antigen is to be produced. In apreferred embodiment, the codons used are “humanized” codons, i.e., thecodons are those that appear frequently in highly expressed human genesas described in Andre et al., “Increased immune response elicited by DNAvaccination with a synthetic gp120 sequence with optimized codon usage,”J. Virol. 72:1497-1503 (1998). Any suitable method of codon optimizationmay be used. Such methods, and the selection of such methods, are wellknown to those of skill in the art. In addition, there are severalcompanies that will optimize codons of sequences, such as Geneart andits website of the same name. Thus, the nucleotide sequences utilized inthe invention can readily be codon optimized.

Another embodiment of the invention also encompasses nucleotidesequences that encode functional and/or equivalent variants andderivatives of the proteins that constitute the carrier or proteins thatare attached to the carrier or are being delivered by the carrier of theinvention and functionally equivalent fragments thereof. For instance,changes in a DNA sequence that do not change the encoded amino acidsequence, as well as those that result in conservative substitutions ofamino acid residues, one or a few amino acid deletions or additions, andsubstitution of amino acid residues by amino acid analogs are those thatwill not significantly affect properties of the encoded polypeptide.Conservative amino acid substitutions are glycine/alanine;valine/isoleucine/leucine; asparagine/glutamine; aspartic acid/glutamicacid; serine/threonine/methionine; lysine/arginine; andphenylalanine/tyrosine/tryptophan. In one embodiment, the variants haveat least 50%, at least 55%, at least 60%, at least 65%, at least 70%, atleast 75%, at least 80%, at least 85%, at least 86%, at least 87%, atleast 88%, at least 89%, at least 90%, at least 91%, at least 92%, atleast 93%, at least 94%, at least 95%, at least 96%, at least 97%, atleast 98% or at least 99% homology or identity to the antigen, epitope,immunogen, peptide or polypeptide of interest.

For purposes of the present invention, sequence identity or homology isdetermined by comparing the sequences when aligned so as to maximizeoverlap and identity while minimizing sequence gaps. In particular,sequence identity may be determined using any of a number ofmathematical algorithms. A nonlimiting example of a mathematicalalgorithm used for comparison of two sequences is the algorithm ofKarlin et al., “Methods for assessing the statistical significance ofmolecular sequence features by using general scoring schemes” Proc.Natl. Acad. Sci. 87: 2264-68 (1990), modified as in Karlin et al.,“Applications and statistics for multiple high-scoring segments inmolecular sequences,” Proc. Natl. Acad. Sci. 90: 5873-77 (1993).

Another example of a mathematical algorithm used for comparison ofsequences is the algorithm of Myers et al., “Optimal alignments inlinear space,” CABIOS 4: 11-17 (1988). Such an algorithm is incorporatedinto the ALIGN program (version 2.0) which is part of the GCG sequencealignment software package. When utilizing the ALIGN program forcomparing amino acid sequences, a PAM120 weight residue table, a gaplength penalty of 12, and a gap penalty of 4 can be used. Yet anotheruseful algorithm for identifying regions of local sequence similarityand alignment is the FASTA algorithm as described in Pearson et al.,“Improved tools for biological sequence comparison,” Proc. Natl. Acad.Sci. 85: 2444-48 (1988).

Advantageous for use according to the present invention is the WU-BLAST(Washington University BLAST) version 2.0 software. WU-BLAST version 2.0executable programs for several UNIX platforms can be downloaded fromon-line. This program is based on WU-BLAST version 1.4, which in turn isbased on the public domain NCBI-BLAST version 1.4 described in Altschulet al., “Local alignment statistics,” Methods in Enzymology, Doolittleed., 266: 460-80 (1996); Altschul et al., J. Mol. Biol., 215: 403-410(1990); Gish et al., Nature Genetics 3: 266-272 (1993); and Karlin etal., Proc. Natl. Acad. Sci. 90: 5873-5877 (1993), the entire contentsand disclosures of which are incorporated herein by reference.

The various recombinant nucleotide sequences and polypeptides associatedwith the invention are made using standard recombinant DNA and cloningtechniques. Such techniques are well known to those of skill in the art.See, for example, Sambrook et al., Molecular Cloning: A LaboratoryManual, second edition, volume 1, 2 and 3 (1989).

In certain embodiments, the polypeptides associated with the presentinvention may be used in vitro (such as using cell-free expressionsystems) and/or in cultured cells grown in vitro in order to produce thepolypeptides which may then be used for various applications such as inthe production of proteinaceous vaccines. For applications where it isdesired that the polypeptides be expressed in vivo, for example when thetransgenes of the invention are used in DNA or DNA-containing vaccines,any vector that allows for the expression of the polypeptides of thepresent invention and is safe for use in vivo may be used.

For the polypeptides associated with the present invention to beexpressed, the protein coding sequence should be “operably linked” toregulatory or nucleic acid control sequences that direct transcriptionand translation of the protein. As used herein, a coding sequence and anucleic acid control sequence or promoter are said to be “operablylinked” when they are covalently linked in such a way as to place theexpression or transcription and/or translation of the coding sequenceunder the influence or control of the nucleic acid control sequence. The“nucleic acid control sequence” can be any nucleic acid element, suchas, but not limited to promoters, enhancers, IRES, introns, and otherelements described herein that direct the expression of a nucleic acidsequence or coding sequence that is operably linked thereto.

Having described the many embodiments of the present invention indetail, it will be apparent that modifications and variations arepossible without departing from the scope of the invention defined inthe appended claims. Furthermore, it should be appreciated that allexamples in the present disclosure, while illustrating many embodimentsof the invention, are provided as non-limiting examples and are,therefore, not to be taken as limiting the various aspects soillustrated.

EXAMPLES

The description of the present invention is enhanced by the variousexamples that follow.

Example 1

Phage heads reassemble a functional DNA packaging machine and packageDNA. Phage T4 gp10 in association with gp11 forms the tail-pins of thebaseplate as described in Leiman et al., “Structure and morphogenesis ofbacteriophage T4,” Cell. Mol. Life. Sci. 60: 2356-70 (2003). Since thetail-pin assembly is the first step of tail assembly, tail structures donot assemble in the absence of gp10. The proteins gp13, gp14, and gp15assemble into a neck that seals off packaged heads, with the gp13protein directly interacting with the portal protein gp20 following DNApackaging and gp14 and gp15 then assembling on the gp13 platform. 10am13am mutants (and analogous mutants in phage λ and other phages) completeall the packaging steps including the cutting of concatemeric DNA anddissociation of the packaging motor. DNA-full phage heads accumulate inthe 10am13 am mutant infected cells, which can be converted toinfectious virions by in vitro complementation with neck and tailproteins. Thus, according to the well-accepted sequential assemblymodels, the heads following completion of DNA packaging are expected tohave the least affinity for the packaging motor but high affinity forthe neck proteins. A novel aspect of the invention relates to it beingthe first time that the packaging machine does not discriminate between“prohead” (FIG. 1, step A) and finished or matured “phage head” (steps Fand G of FIG. 1).

The 10am13 am heads are separated into two major species by CsCl densitygradient centrifugation (DNA sequencing shows that the 10am13 am phagehas TAG amber mutations at residues Trp 430 in gene 10 and Gln 39 ingene 13). Two very closely spaced low-density bands are present at aboutthe middle of the gradient, and a high-density band is located near thebottom of the gradient (FIG. 2). The two close bands, making about 93%of the total heads, contain the same head species but migrate slightlydifferently, probably because the heads in the upper band ate looselyassociated with cell debris (in some purifications, only a broad singleband is seen). Upon further purification by diethylaminoethyl cellulose(DEAE) ion-exchange chromatography, the cell debris contaminants areremoved and the heads elute as a single symmetrical peak (FIG. 3). Boththe head species are resistant to SDS at room temperature (FIG. 4),which means that they are, as expected, in the fully expanded state.Agarose gel electrophoresis shows that the low-density heads contain a˜8-kb DNA band (FIG. 6, lanes 5 and 6) whereas the high-density headscontain near genome length DNA (FIG. 6, lanes 9 and 10). The former isreferred to as “partial” heads and the latter as “full” heads.

Since 13 am mutants accumulate DNA-full heads, the partial heads likelyarose by spontaneous ejection of the packaged DNA from full heads duringthe purification procedures. The full heads are known to be unstable andto spontaneously eject the DNA unless sealed off by neck proteins. Theejected DNA may be digested by the DNAse I present in the buffer,leaving only a small piece of DNA inside the shell. As seen in FIG. 6,the DNA that associates with the partial heads was inside the headbecause it comigrates with the head band (lane 3) and is resistant toDNAse I treatment (lane 4), but upon digestion with proteinase K, theDNA is released and migrates to the 8-kb position (lane 5). It isinteresting that the 8-kb band is consistently observed in severalindependent preparations and is quite compact, suggesting that ejectionstops within a narrow window, after about 95% of the genome is released.This DNA may belong to a specific sequence of the T4 genome because itbinds to the capsid protein and is not ejected. To test this hypothesis,the DNA is extracted from partial heads by phenol and chloroform anddigested with the restriction enzymes EcoRV (six-base cutter) or TaqI(four-base cutter), which can cut the hydroxymethylated and glycosylatedT4 DNA. If the 8-kb DNA belongs to a unique sequence of T4 genome, aseries of discrete bands should result. Alternatively, if each 8-kbpiece belongs to a different part of the genome, the restrictionfragments should not form discrete bands. Results indicate that theproducts migrate as a smear, demonstrating that the retained DNA doesnot have a unique sequence. This is also consistent with the fact thatthe ends of the T4 genome are nearly random, and thus it is not expectedthat the stretch of the genome that is in proximity to the capsidprotein will be of the same DNA in different particles.

The full heads, which make up to about 7% of the total heads, have thepackaged genome relatively stably retained inside the head, presumablybecause either the portal channel is constrained as suggested in Landeret al., “The structure of an infectious P22 virion shows the signal forheadful DNA packaging,” Science 312: 1791-95 (2006) or the DNA ends arenot in close proximity to the entrance of the portal channel. Theseheads slowly release DNA upon storage at 4° C.

The packaging activity of partial and full heads is determined by invitro DNA packaging assay, using the 17am18amrII empty proheads as apositive control. In phage T4, the empty proheads produced bypackaging-defective 17 am mutant infections are mostly of the expandedtype (see lanes 1 and 2 of FIG. 4) since expansion occurs spontaneouslywhen packaging is blocked in vivo. The resultant packaging-naïve emptyexpanded proheads, which package DNA as well or better than theunexpanded proheads, have been used as a positive control in thepackaging assays as referred to in Rao et al., “DNA packaging ofbacteriophage T4 proheads in vitro. Evidence that prohead expansion isnot coupled to DNA packaging,” J. Mol. Biol. 185: 565-578 (1985); Blacket al., “Mechanistic coupling of bacteriophage T4 DNA packaging tocomponents of the replication-dependent late transcription machinery,”J. Biol. Chem. 281: 25635-25643 (2006); and Kondabagil et al., “The DNAtranslocating ATPase of bacteriophage T4 packaging motor,” J. Mol. Biol.363: 786-99 (2006). In bulk packaging assays, both partial and fullheads efficiently pack short DNA fragments (50-766 bp) (FIG. 7).Packaging efficiency of partial heads is about six times higher thanthat of the proheads, the true precursors of DNA packaging in vivo(packaging efficiency is defined as the number of DNA molecules packagedper number of head particles). This may be because the proheads, unlikethe mature heads, are fragile and might have been damaged duringpurification because of irregular expansion in vitro and/or lack of thestabilizing capsid decoration proteins Soc and Hoc as referred to inFokine et al., “Molecular architecture of the prolate head ofbacteriophage T4,” Proc Natl. Acad. Sci. 101: 6003-08 (2004). Theefficiency of partial head packaging is about five to ten times higherthan that of the full heads (FIG. 7, lanes 3 and 6), which maybe becausemost of the full heads may not have any empty space left to accommodateadditional DNA. Accordingly, the partial heads, but not the full heads,packaged the 48.5-kb phage λ DNA (FIG. 8, lanes 7 and 15) or the T4genomic DNA. To confirm that the partial and full heads reassemble theexogenously added packaging motor, the head-gp17 complexes are purifiedand analyzed by Western blotting using polyclonal gp17 antibodies. It isseen that both types of heads reassemble the externally added gp17 (FIG.5). The above findings are reproduced by constructing additional 10am13am phage mutants in which either hoc or soc, or both genes, are alsodeleted.

FIG. 1 shows the major capsid protein assembles around a scaffoldingcore into a prehead. The core is removed by proteolysis to produce anempty unexpanded prohead (A). The unexpanded prohead normally has around shape, but in phage T4 it has angular geometry as referred to inSteven et al., “Conformational changes of a viral capsid protein.Thermodynamic rationale for proteolytic regulation of bacteriophage T4capsid expansion, co-operativity, and super-stabilization by socbinding,” J. Mol. Biol. 228: 870-84 (1992). The packaging motor-DNAcomplex docks on portal and initiates packaging. The prohead expandsafter about 10%-25% of the DNA is packaged (B). After headful packaging,the motor cuts the concatemeric DNA and dissociates from the DNA-fullhead (C). The neck proteins (gp13, gp14, and gp15) assemble on portal toseal off the DNA-full head and provide a platform for tail assembly (D).The various colors of portal represent different conformational states.In promiscuous assembly, the packaging motor assembles on a partial headproduced by ejection of packaged DNA (E) or a full head (G), and refillsthe head with new fragments of DNA ([F] and [G]; new DNA fragments areshown attached to the motor in both the full and partial head stages).

FIG. 2 shows The 10am13 am heads isolated by differential centrifugationfollowed by CsCl gradient centrifugation as described in Example 5. Thetwo closely spaced bands at the top of the gradient contained partialheads that had ejected most of their packaged DNA, save an ˜8-kb piece.The band at the bottom of the gradient contained full heads in which thepackaged T4 genome is stabilized. FIG. 3 shows the purification ofpartial heads by DEAE-Sepharose column chromatography. The two closelyspaced head bands at the top of the CsCl gradient are pooled, dialyzedagainst 10 mM Tris-HCl (pH 7.5), 50 mM NaCl, and 5 mM MgCl2, andpurified by ion-exchange chromatography (AKTA Prime, GE Healthcare). Thecolumn is pre-equilibrated with 50 mM Tris-HCl (pH 7.5) and 5 mM MgCl2,and a linear gradient of 0-300 mM NaCl was applied to elute the boundheads. The peak fractions are pooled, concentrated by filtration, andstored at 4° C. FIG. 4 shows the partial and full heads fully expanded.The purified proheads, partial heads, and full heads are mixed with SDSgel loading buffer and kept at room temperature (“−”) or boilingtemperature (“+”) for 5 min. The samples are then separated by 10%SDS-PAGE, stained with Coomassie blue R, and destained. Note that themajor capsid protein, gp23*(position marked with arrow), was not seen inthe room temperature samples because the expanded heads could not bedissociated into gp23* subunits. FIG. 5 shows partial and full headsreassembled with the exogenous gp17. About 5×1011 proheads, partialheads, or full heads are incubated with purified gp17-K577 (0.3 μM; 50:1ratio of gp17 molecules to gp20 subunits) in a buffer containing 50 mMTris-HCl (pH 7.5), 100 mM NaCl, and 5 mM MgCl2, at room temperature for30 min. The head-gp17 complexes are sedimented by centrifugation at18,000 rpm for 45 min, and the pellet is washed several times to removeany unbound gp17. The proteins are transferred to PVDF membrane, andWestern blotting is performed using polyclonal gp17 antibodies. Theresults are confirmed by doing the same experiment with full-length gp17and a GFP-gp17 fusion protein. Only the gp17-K577 (C-terminal 33 aminoacids of gp17 are deleted) data are shown because gp17-K577 is proteaseresistant and migrates as a single band as opposed to three bands withthe full-length gp17 and GFP-gp17, and also because there is nobackground overlapping band at the same position. The gp17 band in thefull head lane (lane 4) is faint because some of these heads release thepackaged DNA during the procedure, which result in poor recovery of theheads during the centrifugation and washing steps.

FIG. 6 shows partial heads (lanes 3-6), full heads (lanes 7-10), orproheads (lane 12) are treated with DNAse I (37° C., 30 min) and/orproteinase K (65° C., 30 min), as shown by “+” or “−” rows under thefigure, and subjected to agarose gel (0.8% w/v) electrophoresis andstained with cyber green. The molecular size markers λ HindIII (lane 1),λ DNA (lane 2), and T4 DNA (lane 11) are used to determine the size ofthe DNA present in the heads. Partial head lanes 3-6: lane 3, withoutany treatment; lane 4, treated with DNAse I; lane 5, treated withproteinase K; lane 6, treated first with DNAse I and then withproteinase K. Arrow shows the position of the heads stained with cybergreen because they are associated with a ˜8-kb DNA (lane 3). The 8-kbDNA is inside the heads because it is resistant to DNAse I treatment(lane 4) but releases by treatment with proteinase K (lanes 5 and 6).Full head lanes 7-10: lane 7, without any treatment; lane 8, treatedwith DNAse I; lane 9, treated with proteinase K; lane 10, treated firstwith DNAse I and then with proteinase K. Note that the untreated fullheads show, in addition to the head band (arrow), an intensely stainedband in the well plus a smear (lane 7), both of which are removed bydigestion with DNAse I (lane 8). This is because some of the full headsextruded the packaged DNA during storage, which remained complexed withthe head and retained in the well. This is confirmed by treatment withproteinase K, which releases this DNA as well as that packaged inside,producing a single band (lane 9). Treatment first with DNAse I resultsin the digestion of the outside DNA, and subsequent addition ofproteinase K digests the capsids and releases the DNA packaged inside(lane 10). The DNA in lanes 9 and 10 is slightly shorter than thatisolated from phage (lane 11), presumably because a segment of packagedDNA near the portal was accessible to DNAse I digestion [11], [13],[14]. Arrow shows the position of the heads stained with cyber greenbecause they are associated with DNA inside the head (lane 7). Thecontrol 17am18amrII proheads are empty and showed no staining with cybergreen (lane 12) (FIGS. 7 and 8). Packaging of short DNA fragments(50-766 bp) (FIG. 7), or λ DNA (48.5 kb) (FIG. 8) under various reactionconditions, as shown under the figure.

Example 2

Single mature-phage-head-assembled packaging machines refill the capsid.Although Example 1 shows that full heads package DNA, it may be arguedthat a fraction of the full heads ejected DNA during CsCl gradientcentrifugation, converting them into partial heads. To address thisquestion, 10am13 am heads are prepared without the CsCl gradientcentrifugation. The infected cells are lysed in the presence of DNAse I,and phage heads are isolated by differential centrifugation. Theseheads, which contain a mixture of partial heads and full heads, arepackaged with DNA (50- to 766-bp ladder fragments) and are thenseparated by CsCl density gradient centrifugation. This not onlyminimized any DNA ejection from full heads but, more importantly,ensures that only the full heads that package DNA sediment to thehigh-density position (lower band) in the CsCl gradient.

The partial and full head bands (FIG. 9) are extracted from the CsClgradient, treated with proteinase K to release packaged DNA, andelectrophoresed on a 4%-20% polyacrylamide gel. The samples are alsoelectrophoresed prior to proteinase K treatment on an SDS polyacrylamidegel to determine the number of head particles (FIG. 10). As shown inFIG. 11, the full heads package the ladder DNA fragments at similarefficiency as the gradient-purified full heads shown in FIGS. 6, 7 and 8did. Control samples in which the heads are treated the same way exceptthat gp17 and ATP are omitted in the packaging reactions showed nodetectable DNA (FIG. 11, compare packaged lanes 1 and 2 to control lanes3 and 4). The partial heads, as expected, also package DNA at a similarefficiency as the gradient-purified partial heads (FIGS. 6, 7 and 8).Indeed, the packaged partial head band shows a downward shift towardshigher density after packaging (see the packaged left gradient tube inFIG. 9 showing broadening of partial head band towards higher densitywhen compared to the control gradient tube on the right). Theseexperiments indicate that there are no fundamental barriers to packagingshort pieces of DNA into full heads, an observation further confirmed bysingle molecule optical tweezers experiments.

FIG. 9 shows the phage heads are isolated from 10am13 am infected E.coli P301 cells (500 ml culture) by lysis in the presence of DNAse Ifollowed by differential centrifugation. The phage head pelletcontaining a mixture of partial heads and full heads is resuspended in200 μl of 50 mM Tris-HCl (pH 7.5) and 5 mM MgCl2. The sample is splitinto two halves, and larger scale packaging assays are conductedimmediately. The 500-μl packaging reactions contained 100 μl of phageheads, 4.75 μM GFP-gp17, 43 μg of ladder DNA (50-766 bp; NEB), 5% PEGbuffer, and 1 mM ATP. Gp17 and ATP are omitted in the control reaction.After 30 min. of incubation at room temperature, 40 μl (1,000 units) ofBenzonase nuclease (EMD Biosciences) is added to digest unpackaged DNA,and the samples are separated by CsCl density gradient centrifugation.FIG. 10 shows the partial and full head samples from the gradient areelectrophoresed on 10% SDS polyacrylamide gel to analyze for proteinsand to estimate the concentration of particles used in the packagingreactions. Since the concentration of full heads is very low compared tothat of partial heads (roughly 1/10th that of partial heads), the fullheads are concentrated by high-speed centrifugation such that the numberof particles per lane are approximately the same for both full heads andpartial heads (FIGS. 11 and 12). The full (FIG. 11) and partial (FIG.12) head bands from the gradient are treated with proteinase K (18.5 μg;Fermentas) and electrophoresed on 4%-20% polyacrylamide gel inTris-borate buffer (pH 8) to analyze for packaged DNA.

Example 3

Single mature-phage-head-assembled packaging machines refill the capsid.Single molecule experiments are conducted using dual-trap opticaltweezers in a “force-clamp” mode. Head-gp17 packaging complexes areformed in the presence of the non-hydrolyzable analog, ATP-γ-S, andimmobilized on T4-antibody-coated microspheres. The substrate DNAmolecules (10 kb) biotinylated at one end are attached tostreptavidin-coated microspheres. The microspheres are captured inseparate traps and brought into near contact and quickly separated (FIG.13). This “fishing” procedure is repeated until a tether was formed, asevident by a rise in force when the motor captures the DNA. A constantforce of 5 pN is then applied by a feedback loop, and packaging ismeasured as decrease in tether length as a function of time.

The data shows that the packaging rates of the partial-head-assembledpackaging machines (FIG. 14) are similar to those of the empty proheads(FIG. 16) (˜800-1,100 bp/s). As described previously in Zheng et al., “Aconformational switch in bacteriophage p22 portal protein primes genomeinjection,” Mol Cell 29: 376-83 (2008), these rates are about seventimes faster than those of the phi29 packaging machine. The full headsalso packaged DNA but show distinctive features (FIGS. 16, 17 and 18).Some of the heads package the entire 10-kb DNA, and the packaging ratesare similar to those of the partial-head- or prohead-assembled machines(FIG. 16). These heads presumably empty a significant portion of thepackaged DNA during storage, creating room to accommodate a 10-kb piece.A second class of heads package only a short piece of DNA, about 1-3 kb,and then stall, suggesting that these heads may be nearly full and canonly accommodate a small piece (FIG. 17). Interestingly, the packagingrates of these machines are still very high considering that thesemachines presumably packaged into a nearly full head. However, some ofthese machines did not stall completely but instead package slowly(e.g., the top and bottom traces in FIG. 17). A third class of headssimply form tethers, with no translocation evident, suggesting thatthese heads may have had no room left to accommodate additional DNA(FIG. 18). It is interesting that these machines form tethers, anindication that they successfully initiated packaging (as evident by arise in force) but remain in the stalled state for a long period of time(otherwise, the DNA would rapidly slip out under 5 pN of force). Thesedata demonstrate that the packaging machines can efficiently assemble onmature phage heads and refill the capsid, and that the length ofrefilled DNA appears to be dependent upon the amount of space availableinside the capsid.

FIG. 13 shows the dual optical trap setup for single molecule DNApackaging. The T4 head-motor complex and the 10-kb DNA substrate aretethered between two beads, each held in an optical trap and held under5 pN tension as described in Example 7 (FIGS. 14, 15, 16, 17 and 18).Packaging traces showing the packaging of DNA by proheads (FIG. 14),partial heads (FIG. 15), and full heads (FIGS. 16, 17 and 18). “n”represents the number of packaging traces qualitatively showing similarpackaging behavior in that panel.

Example 4

Mature-phage-head-assembled packaging machines undergo multiplepackaging initiations. Short 39-bp Cy5-end-labeled and 83-bpCy3-end-labeled DNAs are packaged into proheads, partial heads, and fullheads using the bulk assay. The packaged heads are immobilized onpolyethylene glycol (PEG)-passivated quartz surface using anti-phage-T4polyclonal antibodies, and total internal reflection microscopy andsingle molecule detection are used to image the fluorescent particles.The “glowing” heads are quantified by determining the average number ofbright spots per area from at least 30 images per sample (FIGS. 19 and21; see FIGS. 23 and 24 for fluorescent images). Consistent with thebulk assays, the average number of bright spots corresponding to partialheads that package the labeled DNA is about 5-fold greater than for theempty proheads, and about 10-fold greater than for the full heads (FIGS.20 and 22). Control experiments, which omitted gp17, had 0-2 brightspots, suggesting that nonspecific fluorescence of any surface-boundmaterial is negligible (the packaged samples were treated with excessDNAse I [10 μg/ml] at room temperature for about 20 h to digest anyunpackaged or nonspecifically bound DNA. Moreover, an analysis of thefluorescence intensity histograms of individual heads that packagefluorescent DNA show that the weighted average intensity for individualpartial head samples is around 5,500 units (arbitrary units), while thesame for proheads was 4,000 units, suggesting that the partial headpackage more DNA molecules than the prohead (FIG. 25). This is furtherquantified by the number of photobleaching steps needed to bleach thefluorescent signal of each spot (FIG. 26). These data show that thepartial heads contain on average five to six DNA molecules per head,whereas the proheads and full heads contain four DNA molecules per head.Thus, the mature phage heads, like the procapsids, can undergo multiplepackaging initiations. The single molecule data also suggest that thelarge difference in packaging efficiency between the partial head, thefull head, and the prohead arises from the inability to initiatepackaging in a large fraction of full heads and proheads. For heads thatare capable of initiating DNA packaging, the number of moleculespackaged is only slightly different between the three species.

FIGS. 19, 20, 21 and 22 show quantification of packaging by singlemolecule fluorescence assay. FIGS. 19 and 21 show fluorescence images ofimmobilized T4 heads packaged with Cy3 (83-bp) and Cy5 (39-bp) DNAs,respectively. One-fourth of the 70 μm×35 lam imaging area is shown ineach case (see FIGS. 23 and 24 for full-size fluorescent images). FIGS.20 and 22 show histograms showing the number of heads packaged with Cy3or Cy5 DNAs. The number of heads showing fluorescence in more than 30images is averaged in each case.

FIG. 23 shows Single molecule fluorescence of heads packaged with Cy539-bp DNA. Representative images of partial heads, proheads, or fullheads packaged with Cy5 39-bp DNA. The imaging area is 70 μm×35 μm.Incubation time, laser intensity, imaging, and analysis parameters arethe same for all samples.

FIG. 24 shows Single molecule fluorescence of heads packaged with Cy383-bp DNA. Representative images of partial heads, proheads, and fullheads packaged with Cy3 83-bp DNA. The imaging area is 70 μm×35 μm.Incubation time, laser intensity, imaging, and analysis parameters arethe same for all samples.

FIG. 25 shows single head intensity for partial heads and proheadspackaged with Cy3 83-bp DNA. Normalized histograms showing single headintensity for partial heads and proheads. Intensity from more than 2,000fluorescent particles was analyzed in each case. The intensity ofpartial heads was brighter than that of proheads. About 46% of imagedpartial heads and only about 29% of proheads have intensity above 5,000,suggesting that the partial heads package more oligonucleotide moleculesthan the proheads.

FIG. 26 shows Photobleaching of a single packaged head. Typicalphotobleaching steps from a single immobilized packaged head, packagedwith multiple Cy5-labeled DNA fragments. Each step corresponds to onepackaged labeled DNA.

Example 5

Purification of 10am13 am heads. The phage heads, both partial heads andfull heads, are isolated from the Escherichia coli P301 infected with10am13 am mutant. Proheads are isolated from the E. coli infected with17am18amrII mutant. Proheads and phage heads are purified according tothe procedures described above. Briefly, the infected cells (500-mlculture) are lysed in 40 ml of Pi—Mg buffer (26 mM Na2HPO4, 68 mM NaCl,22 mM KH2PO4, 1 mM MgSO4 (pH 7.5) containing 10 μg/ml DNAse I andchloroform (1 ml) and incubated at 37° C. for 30 min to digest DNA. Thelysate is centrifuged at 4,300 g for 10 min., and the supernatant iscentrifuged at 34,500 g for 45 min. The supernatant is resuspended in2.5 ml of 50 mM Tris-HCl (pH 7.5) and 5 mM MgCl2, and again subjected tolow- and high-speed centrifugations. The head pellet is then resuspendedin 200 μl of Tris-Mg buffer and purified by CsCl density gradientcentrifugation. The head bands (FIG. 2) are extracted and dialyzedovernight against 10 mM Tris-HCl (pH 7.5), 50 mM NaCl, and 5 mM MgCl2.The two closely spaced bands at the top are pooled and further purifiedby DEAE-Sepharose chromatography (FIG. 3). The peak fractions areconcentrated and stored at 4° C.

Example 6

Bulk in vitro DNA packaging. In vitro DNA packaging assays are performedby the procedure described above. The reaction mixture contains purifiedproheads, partial heads, or full heads (0.5−1×1010 particles), purifiedfull-length gp17 (1.5 μM), and DNA (300 ng of 50- to 766-bp ladder DNA[New England Biolabs], 100 ng of Cy3 83-bp DNA, 50 ng of Cy5 39-bp DNA,or 600 ng of 48.5-kb phage λ DNA). The λ DNA is packaged using a buffercontaining 30 mM Tris-HCl (pH 7.5), 100 mM NaCl, 3 mM MgCl2, and 1 mMATP. The Cy3 and Cy5 DNAs are packaged using the 5% PEG buffer asdescribed above. The packaging reactions are terminated by the additionof DNAse I, and the encapsidated DNAse I-resistant DNA is released bytreatment with proteinase K and analyzed by agarose gel electrophoresis.Each experiment included one to several negative controls that lackedone of the essential packaging components: head, gp17, ATP, or DNA.Packaging efficiency is defined as the number of DNA molecules packagedper the number of head particles used in the packaging reaction.

Example 7

Single-molecule optical tweezers packaging. The packaging complexes areprepared by mixing purified heads (4×109 particles) with purified 1 μMfull-length gp17 and 0.44 μM 125-bp dsDNA “priming” DNA (Z. Z. and V. B.R., unpublished data) in the presence of 1 mM ATP-γ-S in a 10-μlreaction volume consisting of packaging buffer (50 mM Tris-HCl [pH 7.6],100 mM NaCl, and 5 mM MgCl2). The mixture is incubated at 37° C. for 30min. The T4-phage-antibody-coated polystyrene beads (1.5 μl) (0.79 μm indiameter, Spherotech) are added to the above reaction mixture andincubated at 37° C. for 30 min.

The DNA beads are prepared by adding PCR-amplified 10-kb λ DNAbiotinylated at one end to the streptavidin-coated polystyrene beads(0.86 μm in diameter, Spherotech) and incubated at 37° C. for 30 min.The dual-trap optical tweezers are set up and calibrated as described inBustamante et al., “High resolution dual trap optical tweezers withdifferential detection,” Single-molecule techniques: a laboratorymanual, Selvin et al., editors, Woodbury, N.Y.: Cold Spring HarborLaboratory Press. 297-324 (2007); and Chemla et al., “Mechanism of forcegeneration of a viral DNA packaging motor,” Cell 122: 683-692 (2005).Single molecule measurements are taken at 100 Hz in a “force-feedback”mode, where packaging is allowed to occur against a constant force of 5pN. Tether formation and packaging is initiated by infusing packagingbuffer containing 1 mM ATP into the flow cell. To prevent the formationof reactive singlet oxygen species, an oxygen scavenging system is used(100 μg/ml glucose oxidase, 20 μg/ml catalase, and 4 mg/ml glucose). Thecontour length of DNA is calculated from the measured force andextension between the beads using the worm-like chain model assuming apersistence length of 53 nm, a stretch modulus of 1,200 pN and adistance per basepair of 0.34 nm. The velocity of DNA packaging isdetermined from a linear fit of the contour length of DNA over a slidingwindow of 0.1 s (ten data points).

Example 8

Single Molecule Fluorescence of Packaged Heads. Single moleculefluorescence experiments to quantify packaging efficiency of differentheads are performed on a wide field prism-type total internal reflectionmicroscope with a 532 laser (Coherent) for Cy3 excitation or a 630 laser(Melles Griot) for Cy5 excitation. Immobilized capsids are imaged by acharged-coupled-device camera (iXon DV 887-BI; Andor Technology) at100-ms time resolution. A homemade C++ program is used to record andanalyze the images as described in Roy et al., “A practical guide tosingle-molecule FRET,” Nat. Methods 5: 507-16 (2008).

To minimize nonspecific surface binding, clean quartz slides and glasscover slips are surface-passivated with PEG and 3% biotinylated PEG(Laysan Bio) [43]. After assembling the channel, NeutrAvidin (ThermoScientific) is added (0.2 mg/ml), followed by incubation withbiotinylated protein-G (Rockland Immunochemicals) (25 nM) for 30 min atroom temperature. Subsequently, T4 phage antibody (15 nM) is added andincubated for 1 h. The packaged heads with 83-bp Cy3 and 39-bp Cy5 DNAsare applied to separate channels and incubated for 20 min. The packagingreaction mixtures are treated with DNAse I (10 μg/ml) at roomtemperature for about 20 h to digest any unpackaged or nonspecificallybound Cy3 and Cy5 DNAs. The unbound packaged heads are washed off, andimmobilized capsids are imaged in 50 mM Tris-Cl buffer (pH 8), 5% PEG, 5mM MgCl2, 1 mM spermidine, 1 mM putrescene, 60 mM NaCl, and an oxygenscavenger system (0.8% dextrose, 0.1 mg/ml glucose oxidase, 0.02 mg/mlcatalase, and 3 mM Trolox) as further described in Rasnik et al.,“Branch migration enzyme as a Brownian ratchet,” EMBO J. 27: 1727-35(2008).

While the present invention has been disclosed with references tocertain embodiments, numerous modification, alterations, and changes tothe described embodiments are possible without departing from the sphereand scope of the present invention, as defined in the appended claims.Accordingly, it is intended that the present invention not be limited tothe described embodiments, but that it has the full scope defined by thelanguage of the following claims, and equivalents thereof.

1. A method comprising the following steps: (a) attaching a packagingmotor to a carrier, and (b) transferring an exogenous material into aninner compartment of the carrier to thereby form a packaging machine. 2.The method according to claim 1, wherein the carrier is a virusparticle.
 3. The method according to claim 1, wherein the carrier is abacteriophage component.
 4. The method according to claim 1, wherein thecarrier is a bacteriophage derivative.
 5. The method according to claim1, wherein the carrier is a mature capsid shell of a T4 bacteriophage.6.-15. (canceled)
 16. The method according to claim 1, wherein theexogenous material is a nucleic acid.
 17. The method according to claim16, wherein the nucleic acid is DNA.
 18. The method according to claim17, wherein the DNA is either single stranded or double stranded.19.-21. (canceled)
 22. The method according to claim 1, wherein thecarrier comprises a liposomal vesicle.
 23. The method according to claim22, wherein the packaging motor comprises a protein complex.
 24. Themethod according to claim 23, wherein the protein complex comprisesATPase activity.
 25. The method according to claim 22, wherein theprotein complex comprises one or more subunits of gp17 protein.
 26. Themethod according to claim 22, wherein the exogenous material is anucleic acid.
 27. The method according to claim 26, wherein the nucleicacid is DNA.
 28. The method according to claim 27, wherein the DNA iseither single stranded or double stranded.
 29. The method according toclaim 22, wherein the exogenous material is a peptide-like component.30. The method according to claim 22, wherein the exogenous material isa polypeptide or fragment thereof.
 31. The method according to claim 30,wherein the polypeptide or fragment thereof is immunogenic.
 32. Themethod according to claim 31, wherein the polypeptide or fragmentthereof is an antigen.